This invention relates to network testing, and more particularly to a method and apparatus for canceling Far End Cross Talk (FEXT) in an interconnection.
Referring to FIG. 1, a representation of a typical plug/jack combination illustrating a NEXT and FEXT component, a plug 12 interfaces signal ports A′ and B′ to signal ports A and B via jack 14. Referring to a single signal source, Near End Cross Talk (NEXT) is energy from a signal source at port A that is coupled to port B, while Far End Cross Talk (FEXT) is energy from the signal source on port A that is coupled to port B′.
In design of connector jacks, such as an RJ45 jack, for example, the typical goal of a jack designer is to optimize the properties of the jack to minimize return loss, Near End Cross Talk (NEXT) loss and Far End Cross Talk (FEXT) loss. However, because of the interrelated nature of these properties, maximum cancellation of any given parameter is not achieved.
An electrical model of a typical RJ45 plug and of a typical RJ45 jack are show in FIG. 2 and FIG. 3, respectively. The plug consists of 8 connectors, receiving an input cable and providing plug contacts, while the jack has corresponding inputs that connect with the plug contacts and solder leads for soldering to a printed circuit board. The various adjacent lines are mutually inductive and mutually capacitive with their adjacent lines.